You observe the star Deneb at a sextant...

Question 1 of 2707066636eea28f7522a1c51b418

You observe the star Deneb at a sextant altitude (hs) of 48°34.8' on 16 December. The index error is 4.0' off the arc. The height of eye is 58 feet. What is the observed altitude (Ho)?

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Question 1 of 27070

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You observe the star Deneb at a sextant altitude (hs) of 48°34.8' on 16 December. The index error is 4.0' off the arc. The height of eye is 58 feet. What is the observed altitude (Ho)?

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🔍 Key Concepts

• How to correct sextant altitude (hs) to get observed altitude (Ho) • Meaning and sign of index error 4.0' off the arc • Effect of height of eye (dip correction) on the altitude in minutes of arc

💭 Think About

• First, decide whether an index error "off the arc" is added to or subtracted from hs. What does your Bowditch or formula say? • Convert 58 feet of height of eye to dip in minutes of arc. Is dip a plus or minus correction for stars? • For a star, which extra corrections (semi‑diameter, parallax, refraction) are significant or negligible when going from apparent altitude to observed altitude in a typical exam problem?

✅ Before You Answer

• Be sure you apply the correct sign for index error: "off the arc" vs "on the arc" • Confirm that dip is always subtractive from the apparent altitude because your eye is above sea level • Estimate the total correction (index + dip + refraction, etc.) and check whether Ho should be a few minutes greater than, less than, or about the same as hs before choosing a choice